1. Field of Technology and Problem Formulation
It is desirable to have a spread spectrum receiver capable of receiving at least two (or more) types of code division multiple access (CDMA) signals. For example, dual mode GPS (global positioning system)/Galileo receivers must be able to receive both GPS and Galileo signals simultaneously. An obvious approach used so far is combining a GPS receiver and a Galileo receiver, so that some hardware receiving channels are dedicated to receive a GPS signal, and some channels are dedicated to receive a Galileo signal. For example, a 16-channel receiver can have 8 GPS channels and 8 Galileo channels. However, in some situations it might be desirable to receive e.g., 12 Galileo signals and 4 GPS signals due to DOP (dilution of precision) or signal blocking conditions. With the 8 GPS channels plus 8 Galileo channels hardware this is impossible. Therefore, a more flexible multimode operation of the spread spectrum receiver and hardware architecture is desirable.
2. Prior Art
An example of a prior art solution is demonstrated in FIGS. 1 and 2. FIG. 1 is a block diagram representing one example of a typical operation of a global navigation satellite system receiver 10 with dedicated M GPS receiving channel blocks 16-1, 16-2, . . . , 16-M and dedicated N Galileo receiving channel blocks 18-1, 18-2, . . . , 18-N, wherein M is an integer of at least a value of one and N is an integer of at least a value of one. Typical operation includes receiving the radio frequency signal and converting said radio frequency signal to a radio frequency electrical signal 11a by an antenna 11 followed by converting said radio frequency electrical signal 11a to a digital intermediate frequency (IF) signal 14 by a preprocessor 12 and providing said digital IF signal 14 to the dedicated M GPS receiving channel blocks 16-1, 16-2, . . . , 16-M and to the dedicated N Galileo receiving channel blocks 18-1, 18-2, . . . , 18-N, which normally exchange information with the receiver processing block 22 during their operation.
FIG. 2 is a block diagram representing an example of one of the dedicated GPS receiving channel blocks 16-1, 16-2, . . . , 16-M or the dedicated Galileo receiving channel blocks 18-1, 18-2, . . . , 18-N shown in FIG. 1. As seen from FIG. 2, the only difference between the GPS receiving channel blocks 16-1, 16-2, . . . , 16-M and the Galileo receiving channel blocks 18-1, 18-2, . . . , 18-N is in a code generating block 24 which uses a dedicated GPS code generator 28-1 for generating a GPS code signal 42 in case of the GPS receiving channel blocks 16-1, 16-2, . . . , 16-M and a dedicated Galileo code generator 28-2 for generating a Galileo code signal 44 in case of the Galileo receiving channel blocks 18-1, 18-2, . . . , 18-N, respectively. All other components including an integrating and damping block 32 and a residual carrier removing block 25 as well as a frequency control signal 34, a code control signal 38, a data intermediate signal 36, a code and carrier measurement signal 37 and dump signals 46-1, 46-2, . . . , 46-P (P is an integer of at least a value of one) perform identical functions for both GPS and Galileo receiving channel blocks 16-1, 16-2, . . . , 16-M, 18-1, 18-2, . . . , 18-N.
FIGS. 1 and 2 demonstrate only one example for implementing the global navigation satellite system receiver 10 per the prior art. It is noted that details incorporated in blocks 12 and 16-1, 16-2, . . . , 16-M, 18-1, 18-2, . . . , or 18-N are provided for reference only and represent only one example among many others for implementation of these blocks.